This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in searching for and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource.
Such systems generally include a wellhead assembly through which the resource is extracted. These wellhead assemblies may include a wide variety of components that control drilling and/or extraction operations. Such components may include one or more production trees (often referred to as “Christmas trees”), control modules, a blowout preventer system, and various casings, valves, fluid conduits, and the like, that generally facilitate the extraction of resources from a well for transport to the surface. In some applications, trees may also be used to inject materials, such as water and/or long chain polymers, into a well. As can be appreciated, production trees often include certain elements for flow monitoring and control, such as choke valves (often referred to as a “choke”), pressure regulators, and flow meters, as well as chemical injection metering valves, various sensors, and so forth.
During resource extraction, the flow rate of resources extracted from a well may be regulated using flow control devices, such as the above-mentioned choke. Chokes generally control flow rate by using an adjustable choke trim to create a restriction in a flow path, thus throttling the flow. The choke trim may include both a movable component and a fixed component, such as is the case with conventional needle and seat trims (sometimes called gate and seat trims). For example, in this case, the needle may be coupled to an actuator that is able to vary the position of the needle relative to the seat. Accordingly, the restriction provided by the choke trim in this case is variable and depends on the position of the needle relative to the seat. For example, the degree of flow restriction may increase as the needle is moved closer to the seat and may decrease as the needle is moved further away.
The aforesaid needle and seat trim configuration has, however, certain drawbacks. For instance, needle and seat trims have a relatively small throttling area (e.g., a circular region between the needle and seat). Generally, erosion is most heavily concentrated at this throttling point and, therefore, trims having small throttling areas, such as needle and seat trims, tend to be affected by erosion more quickly. Further, when fluid flows through the restriction created by the trim, the fluid velocity increases and accelerates while pressure drops. However, if fluid pressure drops quickly to a level that is less than vapor pressure and then subsequently rises quickly to a level greater than vapor pressure, this can cause the sudden formation and collapse of bubbles, known as cavitation. Cavitation may cause significant wear to the choke and adjacent/associated components.